The objectives of this proposed work are three fold: 1. To corroborate in a larger prospective study our presently completed feasibility study in 13 patients, the findings that dexamethasone suppression adrenal scintiscanning with radioiodinated cholesterol in patients with low renin essential hypertension reveals 4 anatomical-functional images. Uptake of I-131 in one adrenal only is found in an adenoma in one adrenal cortex. Symmetrical uptake early and late is found in macronodular hyperplasia of the adrenal cortex. Symmetrical uptake four days or more after the tracer is found in micronodular hyperplasia. No uptake in either adrenal early or late is found when the adrenal cortices are normal. The blood pressure falls to normal during the administration of spironolactone when the adrenal cortex is abnormal but does not respond significantly to spironolactone when the adrenal cortex is normal. 2. To develop and evaluate radiolabeled enzyme inhibitors of enzymes in the adrenal cortex in an attempt to decrease the time required and radiation dose delivered by radioiodinated cholesterol adrenal imaging agents. 3. For the adrenal medulla; to develop and evaluate the anatomical-functional imaging capabilities of radiolabeled dopamine analogs, reversible enzyme inhibitors of enzymes in the adrenal cortex, and antibodies to dopamine-beta-hydroxylase. The diagnostic ability of the most successful of these radiolabeled imaging agents will be carried out first in patients most at risk for disease of the adrenal medulla, then in patients with normal and high renin hypertension.